Calcium and magnesium transport in the cortical thick ascending limb of Henle's loop: influence of age and gender

Abstract

Previous studies from our laboratory have shown that Ca2+ and Mg2+ absorption in the mouse cortical thick ascending limb of Henle's loop (cTAL) is a passive, paracellular process driven by the transepithelial voltage. The passive permeability of the epithelium is enhanced by peptide hormones. The present study investigated whether divalent cation absorption in the cTAL is influenced by cell maturation and/or gender. For this purpose, mouse cTAL segments were microdissected from kidneys of female and male animals aged 4 and 8 weeks. The microdissected tubules were perfused in vitro at a luminal flow rate of 1.5 to 2.5 nl/min. Transepithelial Na+, Cl-, Ca2+ and Mg2+ net fluxes (JX, pmol.min-1.mm-1) were measured using electron microprobe analysis, and the transepithelial potential difference (PDte) was measured continuously. No differences were found in the PDte, JNa and JCl of the various animal groups but the transepithelial Ca2+ and Mg2+ transport capacity of the cTAL was higher in adults (8 weeks) than in young animals (4 weeks). Furthermore, irrespective of age, transepithelial Ca2+ net absorption was greater in male than in female animals. In contrast, the NaCl transport was maximal at 4 weeks in both genders. We conclude therefore that transepithelial divalent cation absorption in the mouse cTAL is an inductive process influenced by cell maturation and gender. The molecular basis of these inductions remains to be elucidated.

Gender differences in kidney function

“…Also not clear is the observed higher urinary excretion of vitamin C in M mice, because the vitamin C transporters Svct1 and Svct2 that are localized in the mice proximal tubule brush-border exhibited no differences in their expression [124]. The observed M-dominant transepithelial transport capacity for Ca 2+ and Mg 2+ in microdissected cortical thick ascending limbs of Henle (TALH) that appears in mice after puberty [276] is most probably the consequence of an increased expression of the Na + ,K + -2Cl − cotransporter NKCC2 in M. Such a male-predominant expression has at least been demonstrated for the rat [29]. NKCC2 is responsible for the generation of a lumen-positive transepithelial potential difference [60], which drives Ca 2+ and Mg 2+ through paracellin-1 (claudin 16), a protein localized to the tight junctions [210].…”

Gender Differences in the Membrane Transport of Endogenous and Exogenous Compounds

“…With regard to inorganic cations, the transepithelial calcium and magnesium reabsorption in the mouse cortical thick ascending limb of Henle's loop is greater in male than female animals, at both 4 and 8 weeks of age; there were no gender-related differences in NaCl transport (Wittner et al, 1997). There are sex differences in the uptake of inorganic mercury into kidney and motor neurons of mice.…”

Salt and acid-base metabolism in claudin-16 knockdown mice: impact for the pathophysiology of FHHNC patients

“…It is already known that mice show sex differences in Ca 2ϩ and Mg 2ϩ homeostasis (31). Because young female animals are more sensitive to challenges in Na ϩ metabolism (6), we decided to focus on female mice.…”